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Area Forecast Discussion

756
FXUS62 KCHS 260609
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
109 AM EST WED NOV 26 2014

.SYNOPSIS...
A STRENGTHENING AREA OF LOW PRESSURE WILL TRACK NORTHEAST ALONG A
STALLED FRONT OFF THE SOUTHEAST COAST TONIGHT...THEN LIFT AWAY FROM
THE REGION ON WEDNESDAY. HIGH PRESSURE WILL THEN BUILD INTO THE
SOUTHEAST UNITED STATES AND PREVAIL THROUGH EARLY NEXT WEEK.

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
CYCLOGENESIS UNDERWAY RIGHT OFF THE COAST AS PRES FALLS WERE INCREASING
AND SECONDARY LOW PRES TAKING SHAPE. A WET OVERNIGHT WITH MAINLY
LIGHT TO MODERATE RAINS JUST ABOUT EVERYWHERE IN THE FORECAST AREA.
LITTLE/NO CHANGE WITH TEMPERATURES OVERNIGHT. EXPECT A SLOW FALL
LATER TONIGHT AS WINDS BACK TO WNW...HELPING TO PULL COOLER/DRIER
AIR IN TOWARD SUNRISE FROM THE WEST.

LAKE WINDS...STILL EXPECT WINDS TO INCREASE AS THE PRESSURE
GRADIENT TIGHTENS WITH THE DEVELOPING SURFACE LOW OVER THE NEAR
ATLANTIC WATERS AND COLD ADVECTION. GEOSTROPHIC WIND FIELDS OF
40-50 KT AT 1000 MB SHOULD SUPPORT NW WIND GUSTS OF 25 KT OR MORE
IN THE WINDOW FROM AROUND 4-10 AM WEDNESDAY. THUS...LAKE WIND
ADVISORY STILL IN PLACE.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH FRIDAY/...
WEDNESDAY...AN UPPER LEVEL TROUGH WILL BECOME NEGATIVELY TILTED AS
IT PIVOTS INTO THE EASTERN UNITED STATES. AS THIS OCCURS...AN AREA
OF LOW PRESSURE POSITIONED ALONG THE NORTH CAROLINA COAST WEDNESDAY
MORNING WILL RAPIDLY INTENSIFY AS IT LIFTS NORTHEAST FARTHER FROM
THE REGION THROUGH THE DAY. RAINFALL WRAPPING AROUND THE LOW WILL
AFFECT THE AREA IN THE MORNING...WITH DEEP LAYERED MOISTURE AND
STRONG UPPER LEVEL DIVERGENCE IN PLACE. RAINFALL PROBABILITIES WILL
RANGE FROM A CHANCE ACROSS MOST OF SOUTHEAST GEORGIA...TO LIKELY
ACROSS MUCH OF SOUTHERN SOUTH CAROLINA...TO CATEGORICAL ACROSS
NORTHERN PORTIONS OF THE TRI-COUNTY AREA. THE RAINFALL WILL COME TO
AN END BY MIDDAY AS STRONG SHORT WAVE ENERGY ALONG THE LEADING EDGE
OF THE UPPER TROUGH SWINGS THROUGH. SURFACE HIGH PRESSURE WILL THEN
BUILD IN FROM THE GULF OF MEXICO LATE...WITH CLEARING SKIES
EXPECTED. HIGH TEMPERATURES WILL GENERALLY BE IN THE MID AND UPPER
50S ACROSS THE AREA.

WEDNESDAY NIGHT...THE AXIS OF THE UPPER LEVEL TROUGH WILL MOVE
THROUGH...ALONG WITH A REINFORCING COLD FRONT AT THE SURFACE. THE
FRONTAL PASSAGE WILL BE DRY GIVEN LIMITED MOISTURE...BUT A FEW MID
LEVEL CLOUDS COULD ACCOMPANY THE FRONT. WINDS COULD BECOME LIGHT IN
THE EVENING...BUT SHOULD RECOUPLE AS COLD AIR ADVECTION DEVELOPS IN
WAKE OF THE FRONT LATER AT NIGHT. EXPECT LOWS INT EH UPPER 30S TO
AROUND 40.

THURSDAY AND FRIDAY...THE UPPER LEVEL TROUGH WILL BEGIN TO
LIFT OFF TO THE NORTHEAST AS SURFACE HIGH PRESSURE BUILDS INTO THE
REGION FROM THE WEST ON THURSDAY. THE HIGH WILL THEN SETTLE OVER THE
SOUTHEAST UNITED STATES ON FRIDAY. EXPECT MOSTLY CLEAR SKIES ALONG
WITH UNSEASONABLY COOL TEMPERATURES WITH HIGHS IN THE MID AND UPPER
50S AND LOWS IN THE MID 30S INLAND FROM THE IMMEDIATE COAST.

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
HIGH PRESSURE WILL STEADILY SLIP TOWARD THE COASTLINE AND OVER THE
ATLANTIC WATERS THIS WEEKEND INTO EARLY NEXT WEEK...WHILE FLAT
RIDGING DEVELOPS IN THE UPPER LEVELS. EXPECT A STEADILY MODERATING
AIR MASS AND WARMING TREND THROUGH THE PERIOD AS A RESULT. HIGH
TEMPERATURES ON SATURDAY WILL RANGE FROM THE UPPER 50S TO MID
60S...WITH TEMPERATURES PEAKING IN THE UPPER 60S TO AROUND 70
DEGREES BY MONDAY AND TUESDAY AFTERNOONS. LOW TEMPERATURES WILL
ALSO REFLECT THIS WARMING TREND...RANGING FROM THE LOW TO MID 30S
FRIDAY NIGHT...TO THE UPPER 40S BY MONDAY NIGHT. CONDITIONS APPEAR
DRY THROUGH THE EXTENDED PERIOD...AND WILL KEEP RAIN OUT OF THE
FORECAST.

&&

.AVIATION /06Z WEDNESDAY THROUGH SUNDAY/...
WIDESPREAD IFR/RAIN OVERNIGHT WITH OCCASIONAL MVFR CIGS AT TIMES AS
RAINS INTENSITIES FLUCTUATE AT THE TERMINALS. CIGS SHOULD LIFT TO
MVFR WITH RAIN COVERAGE WANING AFTER DAYBREAK AND CERTAINLY BY
MID/LATE MORNING. CLEARING INITIALLY AT KSAV BY MID AFTERNOON WILL
BE SLOWER AT KCHS AS A SECONDARY UPPER DISTURBANCE SWINGS THROUGH.
VFR WEATHER WILL RETURN TO KCHS PERHAPS BY MID AFTERNOON BUT IT
COULD BE JUST A BIT SLOWER. VFR AFTER 00Z THURSDAY AT BOTH
TERMINALS.

WINDS WILL BE GUSTY TODAY AS THE COASTAL STORM DEPARTS AND COOLER
AND DRIER AIR WORKS IN FROM THE WNW.

EXTENDED AVIATION OUTLOOK...VFR CONDITIONS WILL PREVAIL.

&&

.MARINE...
TONIGHT...RAIN STILL EXPECTED OVERNIGHT IN RESPONSE TO DEEPENING
LOW PRESSURE OVER THE LOCAL WATERS AROUND MIDNIGHT...BEFORE IT
HEADS NE THEREAFTER TO A POSITION NORTH OF OUR WATERS BY MORNING.
IN RESPONSE...WINDS AND SEAS WILL QUICKLY CLIMB AS STRONG COLD
ADVECTION DEVELOPS BEHIND THE LOW AND ITS TRAILING COLD FRONT.
THAT ALONG WITH A LARGE RISE-FALL PRESSURE COUPLET WITH RESULTING
ISALLOBARIC PRESSURE RISES ON THE ORDER OF AROUND 1 MB/HOUR LATE
TONIGHT WILL SUPPORT GALE FORCE WINDS ACROSS OUR GA WATERS OUT 60
NM AND ALSO OUR SOUTHERN SC WATERS OUT 20 NM. FOR THE CHARLESTON
HARBOR AND THE CHARLESTON COASTAL WATERS HAVE MAINTAINED A SOLID
SMALL CRAFT ADVISORY...BUT WILL NEED TO WATCH FOR A SMALL WINDOW
OF MARGINAL GALES AFTER DAYBREAK AS THEY TOO GET SOME GOOD
PRESSURE RISES TO OCCUR. HAVE ADDED SLIGHT CHANCE OF THUNDERSTORMS
TO THE OFFSHORE GA /AMD374/ WATERS LATER TONIGHT AS THE LOW
STRENGTHENS AND THAT REGION GETS INTO WARMER/LESS STABLE AIR.

WEDNESDAY THROUGH SATURDAY...AN INTENSIFYING LOW PRESSURE SYSTEM
RAPIDLY PULLING AWAY TO THE NORTHEAST WILL MAINTAIN HAZARDOUS MARINE
CONDITIONS INTO WEDNESDAY MORNING...DUE TO THE ASSOCIATED TIGHT
PRESSURE GRADIENT AND COLD ADVECTION MIXING OVER THE WATERS. GALE
CONDITIONS SHOULD BE ONGOING OVER THE GEORGIA AND FAR SOUTHERN SOUTH
CAROLINA WATERS WEDNESDAY MORNING...WITH SOLID SMALL CRAFT ADVISORY
CONDITIONS ALONG THE CHARLESTON COUNTY COAST AND IN CHARLESTON
HARBOR. CONDITIONS SHOULD BRIEFLY IMPROVE WEDNESDAY AFTERNOON AS THE
LOW PULLS AWAY AND THE GRADIENT RELAXES...BUT ANOTHER SURGE OF COLD
AIR ADVECTION IS EXPECTED WEDNESDAY NIGHT INTO THURSDAY MORNING AS A
STRONG UPPER DISTURBANCE MOVES THROUGH. SMALL CRAFT ADVISORIES COULD
THEREFORE BE NEEDED AGAIN FOR PORTIONS OF THE MARINE ZONES IN THE
LATE WEDNESDAY NIGHT/THURSDAY TIME FRAME. CONDITIONS WILL THEN
IMPROVE FOR FRIDAY AND SATURDAY...AS THE SURFACE HIGH SHIFTS TOWARD
THE WATERS AND THE GRADIENT RELAXES.

&&

.CLIMATE...
KSAV RECORD RAINFALL...OLD RECORD OF 2.01 INCHES SET IN 1899 WAS
BROKEN WITH 2.13 INCHES ON TUESDAY.

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
SC...LAKE WIND ADVISORY FROM 4 AM TO 10 AM EST THIS MORNING FOR
     SCZ045.
MARINE...GALE WARNING FROM 4 AM TO 10 AM EST THIS MORNING FOR AMZ352-
     354-374.
     SMALL CRAFT ADVISORY FROM 4 AM EARLY THIS MORNING TO 4 PM EST
     THIS AFTERNOON FOR AMZ350.
     SMALL CRAFT ADVISORY FROM 4 AM TO 10 AM EST THIS MORNING FOR
     AMZ330.

&&

$$

NEAR TERM...
SHORT TERM...
LONG TERM...
AVIATION...
MARINE...
CLIMATE...






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